Memory circuit and method for routing the memory circuit

ABSTRACT

A memory circuit includes a first row of memory cells, a first word line and a second word line over and electrically coupled to the first row of memory cells, a second row of memory cells aligned with the first row of memory cells along a predetermined direction, and a third word line and a fourth word line over and electrically coupled to the second row of memory cells. The first word line is aligned with the third word line, and the second word line is aligned with the fourth word line. One of the first word line or the second word line is electrically coupled with one of the third word line or the fourth word line. The other one of the first word line or the second word line is electrically decoupled from the other one of the third word line or fourth word line.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No. 12/835,041, filed Jul. 13, 2010, which claims priority of U.S. Provisional Application No. 61/227,994, filed Jul. 23, 2009 which are incorporated herein by reference in their entities.

TECHNICAL FIELD

The present disclosure relates generally to the field of semiconductor circuits, and more particularly, to memory circuits and method for routing word lines of the memory circuits.

BACKGROUND

Memory circuits have been used in various applications. Conventionally, memory circuits can include DRAM, SRAM, and non-volatile memory circuits. A SRAM circuit includes a plurality of memory cells. For a conventional 6-T static memory in which arrays of memory cells are provided, each of the memory cells consists of six transistors. The 6-T SRAM memory cell is coupled with a bit line BL, a bit line bar BLB, and a word line. Four of the six transistors form two cross-coupled inverters for storing a datum representing “0” or “1”. The remaining two transistors serve as access transistors to control the access of the datum stored within the memory cell.

One variation of SRAM designs is a dual-port SRAM structure. The dual-port SRAM structure has speed advantages because it can simultaneously sustain two read operations, two write operations, or one read operation and one write operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the numbers and dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic drawing illustrating an exemplary memory circuit.

FIGS. 2A-2C are schematic drawings illustrating various layers of an exemplary memory array.

FIG. 2D is a schematic cross-sectional view of an exemplary memory array including the poly layer and the M3 layer.

FIGS. 3A-3C are schematic drawings illustrating various layers of another exemplary memory array.

FIG. 3D is a schematic cross-sectional view of an exemplary memory array including the poly layer and the M3 layer.

FIG. 4 is a schematic drawing illustrating various layers of an area of an exemplary memory circuit.

FIG. 5 is a schematic drawing illustrating another exemplary memory circuit having word line sequence exchanged.

FIG. 6 is a schematic drawing illustrating an exemplary memory circuit having word line sequences exchanged in a decoder area and a strap area.

FIG. 7 is a flowchart illustrating an exemplary method for routing word lines of an exemplary memory circuit.

FIG. 8 is a schematic drawing showing a system including an exemplary memory circuit coupled with a processor.

DETAILED DESCRIPTION

Conventionally, a dual-port SRAM cell has two inverters. Each of the inverters is composed of a P-channel MOS transistor in series with an input/output (I/O) node and an N-channel MOS transistor. The node of each inverter is connected to the gates of both transistors of the other inverter. A first I/O transistor and a second I/O transistor are individually connected from a first bit line and a second bit line to the node of one of the inverters. A third I/O transistor and a fourth I/O transistor are individually connected from a first bit line bar and a second bit line bar (always biased oppositely from the corresponding bit line) to the node of the other one of the inverters.

Conventionally, a single row of dual-port SRAM cells can have two word lines. A first word line is coupled with gates of the first I/O transistor and the third I/O transistor of each dual-port SRAM cell. A second word line is coupled with gates of the second I/O transistor and the fourth I/O transistor of each dual-port SRAM cell. Conventionally, the word lines continuously extend in parallel through array regions and word line (WL) decoder regions.

In a memory circuit having 128 word lines, 64 rows of dual-port SRAM cells are disposed from the top to the bottom of the memory circuit. For example, a first row of dual-port SRAM cells can be disposed above and adjacent to a second row of dual-port SRAM cells. Each of the first and second rows of dual-port SRAM cells has the first and second word lines. The second word line of the first row is disposed between the first word line of the first row and the first word line of the second row. During read/write operations, an operating voltage is applied to the first word line of the first row and another operating voltage is applied to the second word line of the second row. The second word line of the first row is grounded. It is found that the operating voltages applied to the first word lines are coupled to the second word line of the first row. The voltage coupling adversely affects the operation of the memory circuit. The coupling effect becomes worse if the word lines of the rows are continuously extended in parallel through all of the array regions and the decoder regions.

Based on the foregoing, memory circuits, systems, and methods for routing word lines of the memory circuits are desired.

It is understood that the following disclosure provides many different embodiments, or examples. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or dispositions discussed.

FIG. 1 is a schematic drawing illustrating an exemplary memory circuit. In FIG. 1, a memory circuit 100 can include at least one memory array, e.g., memory arrays 110 and 120. Each of the memory arrays 110 and 120 can be a dual-port static random access memory (SRAM) array, an embedded dual-port SRAM array, dynamic random access memory (DRAM) array, an embedded DRAM array, a non-volatile memory array, e.g., FLASH, EPROM, E²PROME, and/or other multiple-ports memory array.

The memory array 110 can include at least one memory cell, e.g., memory cells 111 a-111 c, 112 a-112 c, 113 a-113 c, and 114 a-114 c, for storing data. Each of the memory cells 111 a-111 c, 112 a-112 c, 113 a-113 c, and 114 a-114 c can be coupled with a first word line and a second word line. For example, the memory cell 111 a can be coupled with word lines 115 a and 116 a. The memory array 120 can be coupled with the memory array 110. The memory array 120 can include at least one memory cell, e.g., memory cells 121 a-121 c, 122 a-122 c, 123 a-123 c, and 124 a-124 c, for storing data. Each of the memory cells 121 a-121 c, 122 a-122 c, 123 a-123 c, and 124 a-124 c can be coupled with a third word line and a fourth word line. For example, the memory cell 122 a can be coupled with word lines 115 b and 118 b. The word line 115 a can be coupled with the word line 115 b. The word line 115 a can be substantially misaligned from the word line 115 b in a routing direction of the word lines 115 a in the memory array 110. In some embodiments, the word line 115 a can be routed along a row of the memory cells 111 a-111 c of the memory array 110. The word line 115 b can be routed along a row of the memory cells 122 a-122 c of the memory array 120. The row of the memory cells 111 a-111 c is misaligned from the row of the memory cells 122 a-122 c.

It is noted that though merely some memory cells 111 a-114 c and 121 a-124 c are depicted, other memory cells (not shown) can be coupled with the plurality of word lines of the memory circuit 100. A portion of a memory circuit 100 may have 8, 16, 32, 64, 128 or more columns that can be arranged in word widths. In some embodiments, the word lines can be laid out substantially orthogonally to bit lines (not shown). In other embodiments, other arrangements of the word lines and bit lines can be provided.

In some embodiments, the memory circuit 100 can include an area 130. The word line 115 a can be coupled with the word line 115 b at the area 130. The area can include a word line decoder, a word line driver, a strap area, a well-pickup area, and/or any area wherein the word line sequence is capable of being changed and/or at least one word line can jump over another word line. For example, the word line 115 a is the second word line from the top of the memory array 110. The word line 115 b is the third word line from the top of the memory array 120. The sequence of the word lines 115 a and 115 b in the memory arrays 110 and 120 can be exchanged at the area 130.

As noted, the conventional dual-port SRAM circuit has word lines continuously in parallel extending through the array regions and WL decoder region. The charged word lines can couple their voltages to the grounded word line therebetween. The voltage coupling effect can adversely affect the read and/or write operation of the conventional dual-port SRAM circuit.

In contrary to the conventional dual-port SRAM circuit, the memory circuit 100 can exchange word line sequence and/or jump the word lines in the area 130. For example, the word line 115 a can be routed between the word lines 116 a and 117 a in the memory array 110 in FIG. 1. The word line 115 b can be routed between the word lines 117 b and 118 b in the memory array. If voltages are applied to the word lines 116 a and 117 a coupled with the word lines 116 b and 117 b, respectively. The word line 115 a is subjected to the voltage couplings from the word lines 116 a and 117 a in the memory array 110. In the memory array 120, the word line 115 b can be merely subjected to the voltage coupling from the word line 117 b. The word line 115 b can be substantially from the voltage coupling from the word line 116 b since the word line 116 b is distant from the word line 115 b. The coupling effect to the whole word lines 115 a and 115 b of the memory circuit 110 can be desirably reduced by, for example, 50%, compared with the conventional dual-port SRAM circuit. The read and/or write operations of the memory circuit 110 can be desirably achieved.

FIGS. 2A-2C are schematic drawings illustrating various layers of an exemplary memory array. FIG. 2A includes a well layer, an oxide definition (OD) layer, a poly (PO) layer, a contact (CO) layer, and a metal 1 (M1) layer of a portion of an exemplary memory circuit. In FIG. 2A, a portion of a memory array 210 can include memory cells 211 a-211 b and 212 a-212 b. Items of the memory array 210 in FIGS. 2A-2C that are the same items of the memory array 110 in FIG. 1 are indicated by the same reference numerals, increased by 100.

Referring to FIG. 2A, each of the memory cells 211 a-211 b and 212 a-212 b can include a well region 201 a, e.g., an N-well region. The OD layer can include OD regions 202 a-202 h that can be disposed within the memory cell 211 a. Portions of polysilicon lines 215 a_Poly-218 a_Poly can serve as gate nodes of the transistors of the memory cells 211 a-221 b and 212 a-212 b. The contact layer can include contact plugs 203 a-203 d. The M1 layer can include metallic regions 204 a-204 d. The contact plugs 203 a, 203 c, 203 b, and 203 d can couple the polysilicon lines 215 a_Poly-218 a_Poly with the metallic regions 204 a, 204 c, 204 b, and 204 d, respectively.

FIG. 2B includes the M1 layer, a via 1 layer, and a metal 2 (M2) layer. In FIG. 2B, the via 1 layer can include via plugs 205 a-205 d. The M2 layer can include metallic regions 206 a-206 d. In some embodiments, the M2 layer can include bit lines (not labeled) of the memory array 210. The via plugs 205 a-205 d can couple the metallic regions 204 a-204 d with the metallic regions 206 a-206 d, respectively.

FIG. 2C includes the M2 layer, a via 2 layer, and a metal 3 (M3) layer. In FIG. 2C, the via 2 layer can include via plugs 207 a-207 d. The M3 layer can include metallic lines 215 a-218 a. The via plugs 207 a, 207 c, 207 b, and 207 d can couple the metallic regions 206 a, 206 c, 206 b, and 206 d with the metallic lines 215 a-218 a, respectively. It is noted that the word line 115 a-118 a (shown in FIG. 1) can include the metallic lines 215 a-218 a and the polysilicon lines 215 a_Poly-218 a_Poly, respectively.

From the foregoing, the polysilicon line 215 a_Poly can be coupled with the metallic line 215 a through the contact plug 203 a, the metallic region 204 a, the via plug 205 a, the metallic region 206 a, and the via plug 207 a. The polysilicon line 216 a_Poly can be coupled with the metallic line 216 a through the contact plug 203 c, the metallic region 204 c, the via plug 205 c, the metallic region 206 c, and the via plug 207 c. The polysilicon line 217 a_Poly can be coupled with the metallic line 217 a through the contact plug 203 b, the metallic region 204 b, the via plug 205 b, the metallic region 206 b, and the via plug 207 b. The polysilicon line 218 a_Poly can be coupled with the metallic line 218 a through the contact plug 203 d, the metallic region 204 d, the via plug 205 d, the metallic region 206 d, and the via plug 207 d.

FIG. 2D is a schematic cross-sectional view of an exemplary memory array including the poly layer and the M3 layer. In FIG. 2D, the polysilicon lines 215 a_Poly-218 a_Poly and the metallic lines 215 a-218 a can be disposed over a substrate 250. The metal lines 215 a-218 a can be substantially aligned with the polysilicon lines 215 a_Poly-218 a_Poly, respectively, along a direction substantially orthogonal to a surface 251 of the substrate 250.

FIGS. 3A-3C are schematic drawings illustrating various layers of another exemplary memory array. FIG. 3A includes a well layer, an oxide definition (OD) layer, a poly (PO) layer, a contact (CO) layer, and a metal 1 (M1) layer of a portion of an exemplary memory circuit. The well layer, the oxide definition (OD) layer, the poly (PO) layer, the contact (CO) layer, and the metal 1 (M1) layer can be similar to those described above in conjunction with FIG. 2A. In FIG. 3A, a portion of a memory array 320 can include memory cells 321 a-321 b and 322 a-322 b. Items of the memory array 320 in FIGS. 3A-3C that are the same items of the memory array 120 in FIG. 1 are indicated by the same reference numerals, increased by 200.

Each of the memory cells 321 a-321 b and 322 a-322 b can include a well region 301 a, e.g., an N-well region. The OD layer can include OD regions 302 a-302 h disposed within the memory cell 321 a. Portions of polysilicon lines 315 b_Poly-318 b_Poly can serve as gate nodes of the transistors of the memory cells 321 a-321 b and 322 a-322 b. The contact layer can include contact plugs 303 a-303 d. The contact plugs 303 a-303 d can couple the polysilicon lines 315 b_Poly-318 b_Poly with the metallic regions 304 a-304 d, respectively.

FIG. 3B can include the M1 layer, a via 1 layer, and a metal 2 (M2) layer. In FIG. 3B, the via 1 layer can include via plugs 305 a-305 d. The M2 layer can include metallic regions 306 a-306 d. In some embodiments, the M2 layer can include bit lines (not labeled) of the memory array 320. The via plugs 305 a-305 d can couple the metallic regions 304 a-304 d with the metallic regions 306 a-306 d.

FIG. 3C includes the M2 layer, a via 2 layer, and a metal 3 (M3) layer. In FIG. 3C, the via 2 layer can include via plugs 307 a-307 d. The M3 layer can include metallic lines 315 b-318 b. The via plugs 307 a-307 d can couple the metallic regions 306 a-306 d with the metallic lines 315 b-318 b, respectively. It is noted that the word line 115 b-118 b (shown in FIG. 1) can include the metallic lines 215 b-218 b and the polysilicon lines 215 b_Poly-218 b_Poly, respectively.

From the foregoing, the polysilicon line 315 b_Poly can be coupled with the metallic line 315 b through the contact plug 303 a, the metallic region 304 a, the via plug 305 a, the metallic region 306 a, and the via plug 307 a. The polysilicon line 316 b_Poly can be coupled with the metallic line 316 b through the contact plug 303 b, the metallic region 304 b, the via plug 305 b, the metallic region 306 b, and the via plug 207 b. The polysilicon line 317 b_Poly can be coupled with the metallic line 317 b through the contact plug 303 c, the metallic region 304 c, the via plug 305 c, the metallic region 306 c, and the via plug 307 c. The polysilicon line 318 b_Poly can be coupled with the metallic line 318 b through the contact plug 303 d, the metallic region 304 d, the via plug 305 d, the metallic plug 306 d, and the via plug 307 d.

FIG. 3D is a schematic cross-sectional view of an exemplary memory array including the poly layer and the M3 layer. In FIG. 3D, the polysilicon lines 315 b_Poly-318 b_Poly and the metallic lines 315 b-318 b can be disposed over a substrate 350. As noted, the polysilicon line 315 b_Poly is the second polysilicon line from the top of FIG. 3A. The metallic line 315 b coupled with the polysilicon line 315 b_Poly is the third metallic line from the top of FIG. 3C. The metallic line 315 b can be substantially misaligned from the polysilicon line 315 b_Poly along a direction substantially orthogonal to a surface 351 of the substrate 350. In some embodiments, the sequence of the metallic lines 315 b and 317 b can be different from the sequence of the polysilicon lines 315 b_Poly and 317 b_Poly.

FIG. 4 is a schematic drawing illustrating various layers of an area of an exemplary memory circuit. FIG. 4 includes a metal 2 (M2) layer, a via 2 layer, and a metal 3 (M3) layer of an area of an exemplary memory circuit. Items of the memory array 400 in FIG. 4 that are the same items of the memory circuit 100 in FIG. 1 are indicated by the same reference numerals, increased by 300. The M2 layer, via 2 layer, and M3 layer can be similar to those described above in conjunction with FIGS. 2C and 3C.

Referring to FIG. 4, the area 430 can include a word line decoder, a word line driver, a strap area, a well-pickup area, and/or any area wherein the word line sequence is capable of being changed and/or at least one word line can jump over another word line. In the area 430, the M2 layer can include a metallic region 406. The via 2 layer can include via plugs 407 a-407 b. The M3 layer can include metallic lines 415 c, 416 c, 417 c, 417 d, and 418 c. In the area 430, the metallic lines 415 a, 416 a, and 418 a can be coupled with the metallic 415 b, 416 b, and 418 b through the metallic lines 415 c, 416 c, and 418 c, respectively. The metallic lines 416 c and 418 c can be straight lines. The metallic line 415 c includes a couple of turns. With the turns, the metallic line 415 a can be misaligned from the metallic line 415 b in the routing direction of the metallic lines 415 a. The metallic lines 417 a and 417 b can be coupled with the metallic lines 417 c and 417 d, respectively, in the area 430. The metallic line 417 d can be coupled with the metallic line 417 c through the via plugs 407 a and 407 b and the metallic region 406. In some embodiments, the metallic line 415 c can be routed via or jump over the metallic region 406. In other embodiments, the word line including the metallic line 415 c can jump over the word line including the metallic lines 417 c, 417 d and the metallic region 406.

It is noted that the well layer, oxide definition (OD) layer, poly layer, contact layer, via layers, and metal layers described above are mere examples. The memory arrays 210 and 320 and integrated circuit 400 described above in conjunction with FIGS. 2A-2D, 3A-3D, and 4 can include more layers such as a P-well layer, source/drain layer, lightly doped drain (LDD) layer, other contact layer, and/or other metal layer. It is noted that the description above regarding the metallic line 415 c (M3 layer) jumping over the metallic region 406 (M2 layer) is merely exemplary. Different metal layers can be used for the routing and/or jumping the word lines. It is also noted that the layouts of the various layers shown in FIGS. 2A-2C, 3A-3C, and 4 are merely exemplary. One of skill in the art can modify the layouts of the layers of the memory circuit. The scope of the invention is not limited thereto.

FIG. 5 is a schematic drawing illustrating another exemplary memory circuit having word line sequence exchanged. In FIG. 5, word lines 515 a-518 a in a memory array 510 can be coupled with word lines 515 b-518 b in a memory array 520. Items of the memory array 500 in FIG. 5 that are the same items of the memory circuit 100 in FIG. 1 are indicated by the same reference numerals, increased by 400.

Referring to FIG. 5, the word lines 515 a-518 a in a memory array 510 can be misaligned from the word lines 515 b-518 b in a memory array 520 in the routing direction of the word lines 515 a-518 a and 515 b-518 b. In some embodiments, the sequence of the word lines 515 a-518 a in the memory array 510 can be word lines 516 a, 515 a, 517 a, and 518 a from the top. The sequence of word lines 515 b-518 b in the memory array 520 can be word lines 517 b, 516 b, 518 b, and 515 b from the top. The exchange of the sequence of the word lines 515 a-518 a and/or 515 b-518 b can be arranged within an area 530, such as a word line decoder, a word line driver, a strap area, a well-pickup area, and/or any area wherein the word line sequence is capable of being changed and/or at least one word line can jump over another word line. In some embodiments, the exchange of the word line sequence can be performed similar to that described above in conjunction with FIGS. 2A-2D, 3A-3D, and 4.

FIG. 6 is a schematic drawing illustrating an exemplary memory circuit having word line sequences exchanged in a decoder area and a strap area. In FIG. 6, a memory circuit 600 can include at least one memory array, e.g., memory arrays 610 and 620. The memory arrays 610 and 620 can include memory cells 611 a-614 c and 621 a-624 c, respectively. The memory circuit 600 can include a decoder area 630 a and strap areas 630 b-630 c. The memory circuit 600 can include word lines 615 a-615 d coupled with each other. The memory circuit 600 can include word lines 616 a-616 d coupled with each other. The memory circuit 600 can include word lines 617 a-617 d coupled with each other. The memory circuit 600 can include word lines 618 a-618 d coupled with each other.

Referring to FIG. 6, the sequence of the word lines 615 a-618 a from the top in the memory array 610 can be the word lines 616 a, 615 a, 617 a, and 618 a. In one direction, the word line sequence can be exchanged in the strap area 630 c. The sequence of the word lines 615 c-618 c from the top in the memory array 610 can be the word lines 615 c, 616 c, 618 c, and 617 c. In the other direction, the word line sequence can be exchanged in the decoder area 630 a. The sequence of the word lines 615 b-618 b from the top in the memory array 620 can be the word lines 616 b, 617 b, 615 b, and 618 b. After exchanging the word line sequence in the strap area 630 b, the sequence of the word lines 615 d-618 d from the top in the memory array 620 can be the word lines 617 d, 616 d, 618 d, and 615 d.

In some embodiments, the exchange of the word line sequence can be performed similar to that described above in conjunction with FIGS. 2A-2D, 3A-3D, and 4. It is noted that the exchange of the word line sequence described above in conjunction with FIGS. 1, 5, and 6 are merely exemplary. The scope of this application is not limited thereto.

FIG. 7 is a flowchart illustrating an exemplary method for routing word lines of an exemplary memory circuit. In FIG. 7, a method 700 for routing word lines of a memory circuit can include a step 710 routing a first word line and a second word line and a step routing a third word line and a fourth word line.

Referring to FIGS. 1 and 7, the step 710 can route a first word line, e.g., the word line 115 a, and a second word line, e.g., the word line 116 a, of at least one first memory cell, e.g., the memory cells 111 a-111 c, of a first memory array, e.g., the memory array 110. The step 720 can route a third word line, e.g., the word line 115 b, and a fourth word line, e.g., the word line 118 b, of at least one second memory cell, e.g., the memory cells 122 a-122 c, of a second memory array, e.g., the memory array 120. The memory array 120 can be coupled with the memory array 110. The word line 115 a is coupled with the word line 115 b. The word line 115 a is misaligned from the word line 115 b in a routing direction of the word line 115 a in the memory array 110.

In some embodiments, the word line 115 a can be coupled with the word line 115 b at the area 130 of the memory circuit 100. The area 130 includes a word line decoder, a word line driver, a strap area, a well-pickup area, and/or any area wherein the word line sequence is capable of being changed and/or at least one word line can jump over another word line.

FIG. 8 is a schematic drawing showing a system including an exemplary memory circuit coupled with a processor. In FIG. 8, a system 800 can include a processor 810 coupled with a memory circuit 801. The processor 810 is capable of accessing data stored in memory cells of the memory circuit 801. In some embodiments, the processor 810 can be a processing unit, central processing unit, digital signal processor, or other processor that is suitable for accessing data of memory circuit. The memory circuit 801 can be similar to the memory circuits 100, 500, and 600 described above in conjunction with FIGS. 1, 5, and 6, respectively.

In some embodiments, the processor 810 and the memory circuit 801 can be formed within a system that can be physically and electrically coupled with a printed wiring board or printed circuit board (PCB) to form an electronic assembly. The electronic assembly can be part of an electronic system such as computers, wireless communication devices, computer-related peripherals, entertainment devices, or the like.

In some embodiments, the system 800 including the memory circuit 801 can provides an entire system in one IC, so-called system on a chip (SOC) or system on integrated circuit (SOIC) devices. These SOC devices may provide, for example, all of the circuitry needed to implement a cell phone, personal data assistant (PDA), digital VCR, digital camcorder, digital camera, MP3 player, or the like in a single integrated circuit.

In accordance with one embodiment, a memory circuit includes a first row of memory cells, a first word line and a second word line over and electrically coupled to the first row of memory cells, a second row of memory cells aligned with the first row of memory cells along a predetermined direction, and a third word line and a fourth word line over and electrically coupled to the second row of memory cells. The first word line is aligned with the third word line, and the second word line is aligned with the fourth word line. One of the first word line or the second word line is electrically coupled with one of the third word line or the fourth word line. The other one of the first word line or the second word line is electrically decoupled from the other one of the third word line or fourth word line.

In accordance with another embodiment, a memory circuit includes a first row of memory cells, a first word line and a second word line over and electrically coupled to the first row of memory cells, a second row of memory cells adjacent to and in parallel with the first row of memory cells, a third word line and a fourth word line over and electrically coupled to the second row of memory cells, a third row of memory cells aligned with the first row of memory cells along a predetermined direction, a fifth word line and a sixth word line over and electrically coupled to the third row of memory cells, a fourth row of memory cells adjacent to and in parallel with the third row of memory cells, and a seventh word line and an eighth word line over and electrically coupled to the fourth row of memory cells, the seventh word line being aligned with the third word line, and the eighth word line being aligned with the fourth word line. The fourth row of memory cells are aligned with the second row of memory cells along the predetermined direction. The fifth word line is aligned with the first word line, and the sixth word line is aligned with the second word line. One of the first word line or the second word line is electrically coupled with one of the seventh word line or eighth word line. One of the third word line or the fourth word line is electrically coupled with one of the fifth word line or sixth word line.

In accordance with another embodiment, a method of routing word lines of a memory circuit includes routing a first word line and a second word line over and electrically coupled to a first row of memory cells. A third word line and a fourth word line are routed over and electrically coupled to a second row of memory cells, and the second row of memory cells are aligned with the first row of memory cells along a predetermined direction. One of the first word line or the second word line is arranged to be electrically coupled with one of the third word line or fourth word line, and the other one of the first word line or the second word line are left to be electrically decoupled from the other one of the third word line or fourth word line.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A memory circuit comprising: a first row of memory cells; a first word line and a second word line over and electrically coupled to the first row of memory cells; a second row of memory cells aligned with the first row of memory cells along a predetermined direction; and a third word line and a fourth word line over and electrically coupled to the second row of memory cells, the first word line being aligned with the third word line, and the second word line being aligned with the fourth word line, wherein one of the first word line or the second word line is electrically coupled with one of the third word line or the fourth word line; and the other one of the first word line or the second word line is electrically decoupled from the other one of the third word line or fourth word line.
 2. The memory circuit of claim 1, wherein the first word line is electrically coupled with the third word line.
 3. The memory circuit of claim 1, wherein the second word line is electrically coupled with the third word line.
 4. The memory circuit of claim 1, further comprising: a third row of memory cells aligned with the first row of memory cells along the predetermined direction; and a fifth word line and a sixth word line over and electrically coupled to the third row of memory cells, the fifth word line being aligned with the first word line, and the sixth word line being aligned with the second word line, wherein the first word line is electrically coupled with the sixth word line; and the second word line is electrically coupled with the fifth word line.
 5. The memory circuit of claim 1, wherein the first row of memory cells and the second row of memory cells are separated by an area, and the area comprises at least one of a word line decoder, a word line driver, a strap area, a well-pickup area, or a combination thereof.
 6. The memory circuit of claim 1, wherein memory cells of the first and second rows of memory cells are dual port static random access memory (SRAM) cells.
 7. A memory circuit comprising: a first row of memory cells; a first word line and a second word line over and electrically coupled to the first row of memory cells; a second row of memory cells adjacent to and in parallel with the first row of memory cells; a third word line and a fourth word line over and electrically coupled to the second row of memory cells; a third row of memory cells aligned with the first row of memory cells along a predetermined direction; a fifth word line and a sixth word line over and electrically coupled to the third row of memory cells, the fifth word line being aligned with the first word line, and the sixth word line being aligned with the second word line; a fourth row of memory cells adjacent to and in parallel with the third row of memory cells, the fourth row of memory cells being aligned with the second row of memory cells along the predetermined direction; and a seventh word line and an eighth word line over and electrically coupled to the fourth row of memory cells, the seventh word line being aligned with the third word line, and the eighth word line being aligned with the fourth word line, wherein one of the first word line or the second word line is electrically coupled with one of the seventh word line or eighth word line; and one of the third word line or the fourth word line is electrically coupled with one of the fifth word line or sixth word line.
 8. The memory circuit of claim 7, wherein: the other one of the first word line or the second word line is electrically coupled with the other one of the fifth word line or sixth word line; and the other one of the third word line or the fourth word line is electrically coupled with the other one of the seventh word line or eighth word line.
 9. The memory circuit of claim 7, wherein the first, second, third, and fourth word lines comprise four corresponding polysilicon lines and four corresponding metal lines extending along the predetermined direction.
 10. The memory circuit of claim 9, wherein a sequence of the four polysilicon lines corresponding to the first, second, third, and fourth word lines is different from that of the four metal lines.
 11. The memory circuit of claim 7, wherein: the first word line is electrically coupled with the fifth word line; the second word line is electrically coupled with the seventh word line; the third word line is electrically coupled with the sixth word line; and the fourth word line is electrically coupled with the eighth word line.
 12. The memory circuit of claim 7, wherein: the first word line is electrically coupled with the seventh word line; the second word line is electrically coupled with the fifth word line; the third word line is electrically coupled with the eighth word line; and the fourth word line is electrically coupled with the sixth word line.
 13. The memory circuit of claim 7, further comprising: a fifth row of memory cells aligned with the first row of memory cells along the predetermined direction; and a ninth word line and a tenth word line over and electrically coupled to the fifth row of memory cells, the ninth word line being aligned with the first word line, and the tenth word line being aligned with the second word line, wherein the first word line is electrically coupled with the tenth word line; and the second word line is electrically coupled with the ninth word line.
 14. The memory circuit of claim 7, wherein memory cells of the first, second, third, and fourth rows of memory cells are dual port static random access memory (SRAM) cells.
 15. The memory circuit of claim 7, wherein the first row of memory cells and the third row of memory cells are separated by an area, and the area comprises at least one of a word line decoder, a word line driver, a strap area, a well-pickup area, or any combinations thereof.
 16. A method of routing word lines of a memory circuit, the method comprising: routing a first word line and a second word line over and electrically coupled to a first row of memory cells; routing a third word line and a fourth word line over and electrically coupled to a second row of memory cells, the second row of memory cells being aligned with the first row of memory cells along a predetermined direction; and arranging one of the first word line or the second word line to be electrically coupled with one of the third word line or fourth word line and leaving the other one of the first word line or the second word line to be electrically decoupled from the other one of the third word line or fourth word line.
 17. The method of claim 16, further comprising: routing a fifth word line and a sixth word line over and electrically coupled to a third row of memory cells, the third row of memory cells being adjacent to and in parallel with the first row of memory cells; routing a seventh word line and a eighth word line over and electrically coupled to a fourth row of memory cells, the fourth row of memory cells being adjacent to and in parallel with the second row of memory cells, and the third row of memory cells being aligned with the fourth row of memory cells along the predetermined direction; arranging the other one of the first word line or the second word line to be electrically coupled with one of the seventh word line or eighth word line; and arranging the other one of the third word line or the fourth word line to be electrically coupled with one of the fifth word line or sixth word line.
 18. The method of claim 17, further comprising: arranging the other one of the fifth word line or sixth word line to be electrically coupled with the other one of the seventh word line or eighth word line.
 19. The method of claim 16, further comprising: routing a fifth word line and a sixth word line over and electrically coupled to a third row of memory cells, the third row of memory cells being aligned with the first row of memory cells along the predetermined direction, the fifth word line being aligned with the first word line, and the sixth word line being aligned with the second word line; arranging the first word line to be electrically coupled with the sixth word line; and arranging the second word line to be electrically coupled with the fifth word line.
 20. The method of claim 16, wherein the routing the first word line comprising: routing a polysilicon line for the first word line over a substrate; and routing a metal line for the first word line, the polysilicon line and the metal line are misaligned in a direction perpendicular to a surface of the substrate. 